Communication terminal

ABSTRACT

A communication terminal optimally switches between the use of multicast reception and unicast reception, in consideration of the mobile radio environment of each terminal. For example, received signal strength indicator information is acquired at a received signal strength indicator information acquisition time calculated using a content reception time. Either multicast reception or unicast reception is selected according to the acquired received signal strength indicator information and content reception is performed. An optimal reception system can be selected and reception failure can be reduced. In addition, by performing a dynamic switching of reception methods as such, the base station-end can perform multicast delivery rather than unicast delivery when possible to communication terminals in favorable mobile radio environments, thereby significantly reducing the traffic load placed on communication paths.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of Ser. No. 11/441,714, filed May 25,2006, which claims the benefit of priority from Japanese PatentApplication No. 2005-155203, filed May 27, 2005, the entire contents ofwhich are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a communication terminal that selectsan optimal reception system and reduces reception failure.

2. Description of the Related Art

In recent years, services for delivering video and audio contents, etc.to a plurality of users by broadcast via a wired broadband circuit, suchas Asymmetric Digital Subscriber Line (ADSL) and Fiber-To-The-Home(FTTH), are becoming popular. IP multicast technology, represented byInternet Group Management Protocol (IGMP), is used in multicast servicessuch as these.

The IP multicast technology is an extremely effective means inone-to-many communication where the same contents are transmittedsimultaneously to a plurality of receivers. Thus, the use of thistechnology is growing, not only in the field of wired communication, butalso in the field of wireless communication. Technology as such is, forexample, disclosed in the Japanese Laid-open Patent Publication No.2001-308856.

In addition, as disclosed, for example, in the publication of TheInstitute of Electronics, Information and Communication EngineersJournal November 2002, Vol. J85-B, No. 11, p 1823 to 1824, acommunication technology, referred to as reliable multicast, thatenhances reliability through the combined use of one-to-one unicastcommunication and one-to-many multicast communication is also known.

A reason for the combined use of multicast communication and unicastcommunication in the reliable multicast system is because multicastcommunication is favorable at times and unicast communication isfavorable at other times depending on the mobile radio environment ofindividual terminals. For example, in a one-to-many, single-directioncommunication such as the multicast communication, the transmission rateis generally unilaterally decided by the transmitting-end. In this case,the probability of failure is high when multicast reception is beingcarried out because a communication terminal that has a weak receivedsignal strength indicator and is strongly influenced by the effects oferror factors, such as noise, interference, and attenuation. Therefore,it is preferable to perform reception for a terminal in a degradedmobile radio environment using the transmitting-end to acquirenegotiation by one-to-one unicast and establishing communicationsuitable for the reception mobile radio environment of that terminal.

However, the method of combining and using multicast communication andunicast communication in the reliable multicast system is unique. Inother words, when a reception terminal performs multicast communication,communication is performed through a predetermined combinationregardless of the terminal being in an environment with high receptionfailure probability and as a result, reception failure may occur.

SUMMARY OF THE INVENTION

In accordance with an aspect of the present invention, there is provideda communication terminal which is capable of receiving a content filecomprising: a content reception time acquisition means for acquiring acontent reception time; a multicast reception means for receivingcontent by multicast delivery; a unicast reception means for receivingcontent by unicast delivery; a received signal strength indicatoracquisition time calculation means for calculating a received signalstrength indicator information acquisition time using the contentreception time acquired by the content reception time acquisition means;a received signal strength indicator acquisition means for acquiringreceived signal strength indicator information from a signal received bythe communication terminal at the received signal strength indicatoracquisition time calculated by the received signal strength indicatoracquisition time calculation means; and a reception method judgmentmeans for selecting either the multicast reception means or the unicastreception means according to the received signal strength indicatorinformation acquired by the received signal strength indicatoracquisition means and instructing content reception.

In accordance with another aspect of the present invention, there isprovided a communication terminal which is capable of receiving contentfiles, comprising: a multicast reception means for receiving content bymulticast delivery; a unicast reception means for receiving content byunicast delivery; a content reception completion judgment means forjudging whether a content reception was successful; a received signalstrength indicator acquisition means for acquiring received signalstrength indicator information from a signal received by thecommunication terminal; and a reception method judgment means forselecting either the multicast reception means or the unicast receptionmeans according to the received signal strength indicator informationacquired by the received signal strength indicator acquisition means andinstructing content reception, when the content reception completionjudgment means judges that the content reception was not completedsuccessfully.

In accordance with another aspect of the present invention, there isprovided a communication terminal which is capable of receiving contentfiles, comprising: a content reception time acquisition means foracquiring a content reception time; a multicast reception means forreceiving content by multicast delivery; a unicast reception means forreceiving content by unicast delivery; a remaining battery levelacquisition means for acquiring remaining battery level information onthe remaining battery level for driving the communication terminal; aremaining battery level acquisition time calculation means forcalculating the time at which the remaining battery level information isacquired using the content reception time information; a remainingbattery level acquisition time judgment means for judging whether thecurrent time is the time at which the remaining battery levelinformation is acquired; and a reception method judgment means forselecting either the multicast reception means or the unicast receptionmeans according to a judgment result of a reception method selectionusing the remaining battery level information and instructing contentreception.

In accordance with another aspect of the present invention, there isprovided a communication terminal which is capable of receiving contentfiles, comprising: a multicast reception means for receiving content bymulticast delivery; a unicast reception means for receiving content byunicast delivery; a content reception completion judgment means forjudging whether a content reception was successful; a remaining batterylevel acquisition means for acquiring remaining battery levelinformation on the remaining battery level for driving the communicationterminal; and a reception method judgment means for selecting either themulticast reception means or the unicast reception means according to ajudgment result of a reception method selection using the remainingbattery level information and instructing content reception, when thecontent reception completion judgment means judges that the contentreception was not completed successfully.

In accordance with another aspect of the present invention, there isprovided a communication terminal which is capable of receiving contentfiles, comprising: a content reception time acquisition means foracquiring a content reception time; a multicast reception means forreceiving content by multicast delivery; a unicast reception means forreceiving content by unicast delivery; a remaining battery levelacquisition means for acquiring remaining battery level information onthe remaining battery level for driving the communication terminal; aremaining battery level acquisition time calculation means forcalculating the time at which the remaining battery level information isacquired using the content reception time information; a remainingbattery level acquisition time judgment means for judging whether thecurrent time is the time at which the remaining battery levelinformation is acquired; a remaining battery level judgment means forjudging whether or not there is remaining battery power using theremaining battery level information; a received signal strengthindicator acquisition means for acquiring received signal strengthindicator information from a signal acquired by the communicationterminal; and a reception method judgment means for selecting either themulticast reception means or the unicast reception means, according to ajudgment result of a reception method selection using the receivedsignal strength indicator information and the judgment result of theremaining battery level judgment means, and instructing contentreception.

In accordance with another aspect of the present invention, there isprovided a communication terminal which is capable of receiving contentfiles, comprising: a multicast reception means for receiving content bymulticast delivery; a unicast reception means for receiving content byunicast delivery; a content reception completion judgment means forjudging whether a content reception was successful; a remaining batterylevel acquisition means for acquiring remaining battery levelinformation on the remaining battery level for driving the communicationterminal; a remaining battery level judgment means for judging whetheror not there is remaining battery power using the remaining batterylevel information, when the content reception completion judgment meansjudges that the content reception was not completed successfully; areceived signal strength indicator acquisition means for acquiringreceived signal strength indicator information from a signal acquired bythe communication terminal; and a reception method judgment means forselecting either the multicast reception means or the unicast receptionmeans, according to a judgment result of a reception method selectionusing the received signal strength indicator information and thejudgment result of the remaining battery level judgment means, andinstructing content reception, when the content reception completionjudgment means judges that the content reception was not completedsuccessfully.

The above and further novel features of the present invention will morefully appear from the following detailed description when the same isread in conjunction with the accompanying drawings. It is to beexpressly understood, however, that the drawings are for the purpose ofillustration only and are not intended as a definition of the limits ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a configuration according to the firstembodiment of the present invention;

FIG. 2 is a flowchart of a content reception operation according to thefirst embodiment;

FIG. 3 is a block diagram of a configuration according to the secondembodiment;

FIG. 4 is a flowchart of a content reception operation according to thesecond embodiment; and

FIG. 5A and FIG. 5B are diagrams of display examples of a contentreception results according to the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will hereinafter be described in detail withreference to the preferred embodiments shown in the accompanyingdrawings.

A. First Embodiment

A-1. Configuration

FIG. 1 is a diagram of a configuration of a communication terminal 100according to the first embodiment of the present invention. Thecommunication terminal 100 comprises constituent parts 101 to 114. Awireless section 102 performs wireless communication via a transmittingand receiving antenna 101. Furthermore, the wireless section 102incorporates a modulation/demodulation circuit and communicationprotocols required to utilize communication systems, such as timedivision multiple access (TDMA), code division multiple access (CDMA),and wireless local area network (LAN). A communication control section103 acquires received signal strength indicator information, etc. fromthe wireless section 102 and controls and manages the communicationstate according to the state of the terminal.

A content delivery processing section 104 is a module that performs astreaming reception process, a file download-storage process of videoand audio content files, etc. The content delivery processing section104 comprises a content reception time storage section 108, a multicastreception processing section 109, a unicast reception processing section110, a received signal strength indicator acquisition time calculationprocessing section 111, a received signal strength indicator acquisitiontime judgment section 112, a received signal strength indicatorinformation acquisition section 113, and a reception method judgmentsection 114.

The content reception time storage section 108 receives and storescontent delivery starting time information. The multicast receptionprocessing section 109 performs a processing for receiving content bymulticast delivery. The unicast reception processing section 110performs a processing for receiving content by unicast delivery. Thereceived signal strength indicator acquisition time calculationprocessing section 111 calculates the time at which a received signalstrength indicator is acquired. The received signal strength indicatoracquisition time judgment section 112 judges whether the time at whichthe received signal strength indicator is acquired matches the currenttime. The received signal strength indicator information acquisitionsection 113 acquires the received signal strength indicator informationfrom the communication control section 103. The reception methodjudgment section 114 judges whether or not the received signal strengthindicator information is larger than an arbitrary threshold x, andselects the reception system based on the judgment result of whether toreceive by multicast or to receive by unicast.

A user interface section 105 prescribes a method of displayinginformation to the user and a user data input system. An input section106 is a module that receives input from the user and notifiesoperational information, such as content reception termination andcontent reproduction start, from the user to the user interface 105. Adisplay section 107 displays the information received from the userinterface 105. For example, antenna bars indicating the received signalstrength indicator information and a “successful content reception” whena content reception is successful are displayed.

A-2. Operations

Next, a content reception operation performed by the content deliveryprocessing section 104 comprising a multicast delivery function and aunicast delivery function is explained with reference to FIG. 2. First,at Step S200, the content reception time storage section 108 acquirescontent reception starting time information from a delivery source suchas a base station. In a system where content can be received at a timedesired by the terminal rather than the delivery time being specified bythe delivery source, the reception time of which notification is givento the delivery source from the communication terminal is stored in thecontent reception time storage section 108.

Next, at Step S201, the received signal strength indicator acquisitiontime calculation processing section 111 calculates the time at which thereceived signal strength indicator information is acquired using thecontent reception starting time information. For example, when thereceived signal strength indicator information s seconds before thestart of content reception is referenced, the time at which the receivedsignal strength indicator information is acquired can be calculated bysubtracting s seconds from the reception starting time information.Then, at Step S202, whether the current time matches the time at whichthe received signal strength indicator is acquired is judged by thereceived signal strength indicator acquisition time judgment section112.

If judged at Step S202 that the times do not match, or namely, it is nottime to acquire received signal strength indicator information, thereceived signal strength indicator acquisition time judgment section 112judges again whether the current time matches the time at which thereceived signal strength indicator is acquired at Step S202. If judgedat Step S202 that the times match, or namely, it is time to acquirereceived signal strength indicator information, the communicationcontrol section 103 in the received signal strength indicatorinformation acquisition section 113 acquires the received signalstrength indicator information at Step S203.

Here, the received signal strength indicator information refers to, forexample, a received signal strength indicator (RSSI), a ratio of pilotsignal energy to total energy (Ec/Io) and a carrier-to-interferenceenergy ratio (C/I) that quantitatively express the positive and negativeaspects of a mobile radio environment. These indicators per se do notnecessarily have to be used and the number of antenna bars, etc. canalso be used.

At Step S204, whether the received signal strength indicator informationacquired at Step S203 is larger than the arbitrary threshold x is judgedin the reception method judgment section 114. If judged at Step S204that the received signal strength indicator is larger than the arbitrarythreshold x, the process proceeds to Step S205 and reception isperformed by multicast delivery in the multicast reception processingsection 109.

On the other hand, if judged that the received signal strength indicatoris smaller the arbitrary threshold x, the process proceeds to Step S206and reception is performed by unicast delivery in the unicast receptionprocessing section 110. In other words, the content delivery source suchas a base station is notified of a unicast reception request and contentreception is performed through negotiation. When judged that thereceived signal strength indicator is larger than the arbitrarythreshold x at Step S204, the mobile radio environment of thecommunication terminal is favorable, and thus, the probability that thecontent can be received successfully by multicast delivery is high.

At the same time, if judged that the received signal strength indicatoris smaller than the arbitrary threshold x, contents may not be receivedsuccessfully using multicast delivery because the mobile radioenvironment of the communication terminal is poor. In other words, aninefficient situation in which a multicast reception is performed in apoor mobile radio environment where a high probability of lost packetsis foreseeable can be circumvented and an efficient retransmissionrequest can be made. In addition, the base station-end can alsosignificantly reduce the traffic load placed on communication paths byperforming multicast delivery rather than unicast delivery whenpossible.

Although the judgment means for whether to perform multicast receptionor unicast reception at Step S204 uses the received signal strengthindicator information of the communication terminal s seconds prior tothe start of content reception, other methods can be implemented. Forexample, the calculated average value of the received signal strengthindicator from m seconds to n seconds prior to the start of contentreception can be used; the mobile radio environment state can be judgedfrom the number of antenna bars; or the received signal strengthindicator information used to calculate the number of antenna bars canbe used. Furthermore, fluctuations in the received signal strengthindicators, or namely, received signal strength indicator variation, canbe calculated by calculating a standard deviation of the received signalstrength indicator from i seconds to j seconds prior to the start ofcontent reception. Then, whether multicast reception is performed orunicast reception is performed can be judged using the standarddeviation as a threshold. If the standard deviation is large, thevariation in the received signal strength indicators is significant. Themobile radio environment is determined to be unstable, and thus, unicastreception is performed. On the other hand, if the standard deviation issmall, the variation in the received signal strength indicators issmall. Accordingly, the mobile radio environment is determined to bestable, and thus, multicast reception is performed.

In addition, whether to perform multicast reception or unicast receptioncan be judged by a combination of the received signal strength indicatorand the standard deviation allowing a more reliable judgment.

As an alternative means of the received signal strength indicatorinformation, remaining battery level can be used as well. When theremaining battery level is higher than a threshold y, or namely, whenthe terminal can still be driven for a long period of time, multicastreception is performed. When the remaining battery level is lower than acertain threshold, or in other words, the terminal cannot be driven fora long period, unicast reception that can almost certainly receivecontent is performed. In this way, efficient power consumption can beperformed and user-friendliness can be enhanced. The present embodimentcan be actualized by replacing all received signal strength indicatorinformation in FIG. 1 and FIG. 2 with the remaining battery level. Theprocessing flow in this case is the same as that using received signalstrength indicator information.

In addition, when the remaining battery level is lower than a certainthreshold, or in other words, when the terminal cannot be driven for along period, unicast reception that can almost certainly receive contentis performed. However, if the remaining battery level is larger than acertain threshold, or namely, the terminal can still be driven for along period, multicast reception is not necessarily performed. This isbecause it cannot be said with certainty that the probability of asuccessful completion of a multicast content reception is high in aterminal that is in a poor mobile radio environment regardless of a highremaining battery level.

Therefore, when the remaining battery level is higher than an arbitrarythreshold y, or namely, when the terminal can be driven for a longperiod, it is effective for the terminal whether multicast reception isperformed or unicast reception is performed should be determined againby using the received signal strength indicator information, asdescribed in the present embodiment. In other words, the judgment ofwhether unicast reception is performed or multicast reception isperformed when receiving content in a content reception systemcomprising two reception functions, the multicast reception and theunicast reception, is made using remaining battery level information andreceived signal strength indicator information, and thus, the terminalof this invention can realize further reduction in the power consumptionof the terminal and to provide a more efficient service to the user.

B. Second Embodiment

Next, a second embodiment is explained with reference to FIG. 3 to FIGS.5A and 5B.

B-1. Configuration

First, FIG. 3 is a block diagram of a configuration of a communicationterminal 300 according to the second embodiment of the presentinvention. The communication terminal 300 comprises constituent parts301 to 312. A wireless section 302 performs wireless communication via atransmitting and receiving antenna 301. Furthermore, the wirelesssection 302 incorporates a modulation/demodulation circuit andcommunication protocols required to utilize communication systems, suchas TDMA, CDMA, and wireless LAN. A communication control section 303 isa module that acquires received signal strength indicator information,etc. from the wireless section 302 and controls and manages thecommunication state according to the state of the terminal.

A content delivery processing section 304 is a module that performs astreaming reception process and a file download and storage process ofvideo and audio content files, etc. The content delivery processingsection 304 comprises a multicast reception processing section 308, aunicast reception processing section 309, a content reception completionjudgment section 310, a received signal strength indicator acquisitiontime judgment section 311, and a reception method re-judgment section312.

The multicast reception section 308 performs a processing for receivingcontent by multicast delivery. The unicast reception processing section309 performs a processing for receiving content by unicast delivery. Thecontent reception completion judgment section 310 judges whether acontent reception has been successfully completed. The received signalstrength indicator information acquisition section 311 acquires thereceived signal strength indicator information from the communicationcontrol section 303. The reception method re-judgment section 312 judgeswhether or not the received signal strength indicator information islarger than an arbitrary threshold x and selects the reception systembased on the judgment result of whether to perform multicast receptionor to perform unicast reception.

A user interface section 305 prescribes a method of displayinginformation to the user and a user data input system. An input section306 is a module that receives input from the user. Also, the inputsection 306 notifies the user operational information of how to operatethe terminal, such as content reception termination and contentreproduction start, from the user to the user interface 305. A displaysection 307 displays the information received from the user interface305. For example, antenna bars indicating the received signal strengthindicator information and a “successful content reception” when acontent reception is successful are displayed.

B-2. Operations

Next, a content reception operation of the content delivery processingsection 304 is explained with reference to FIG. 4.

First, at Step S400, the multicast reception processing section 308 inthe content delivery processing section 304 performs content reception.Next, the process proceeds to Step S401 and the content receptioncompletion judgment section 310 judges whether content reception hasbeen successfully completed. If judged at Step S401 that the contentreception has been successfully completed, or namely, the contentreception is successful in Step S402, the multicast reception processingsection 308 performs processing to complete the content reception.

If judged at Step S401 that the content reception has been abnormallyterminated, or namely, the content reception has failed, the processproceeds to a content re-reception process. If judged that contentreception has failed, the process proceeds to Step S403 and the receivedsignal strength indicator information during content reception failureis acquired from the communication control section 303 by the receivedsignal strength indicator information acquisition section 311. Here, thereceived signal strength indicator information refers to, for example, areceived signal strength indicator (RSSI), a ratio of pilot signalenergy to total energy (Ec/Io), and a carrier-to-interference energyratio (C/I) that quantitatively express the positive and negativeaspects of a mobile radio environment. These indicators per se do notnecessarily have to be used and the number of antenna bars, etc. canalso be used.

Then, at Step S404, the reception method re-judgment section 312 judgeswhether the received signal strength indicator information acquired atStep S403 is larger than the arbitrary threshold x. If judged at StepS404 that the received signal strength indicator is larger than thearbitrary threshold x, the multicast reception processing section 309performs reception by multicast delivery at Step S405. In other words,the content delivery source such as the base station is notified of amulticast reception request and content reception is performed throughnegotiation.

On the other hand, if judged at Step S404 that the reception signalstrength indicator information is smaller than the arbitrary thresholdx, the unicast reception processing section 310 performs a unicastreception at Step S406. In other words, the content delivery source suchas the base station is notified of a unicast reception request andcontent reception is performed through negotiation.

If judged at Step S404 that the received signal strength indicatorinformation is larger than the arbitrary threshold x, content receptionis judged to have failed regardless of the favorable mobile radioenvironment of the communication terminal and content reception isattempted again by multicast delivery. On the other hand, if judged thatthe received signal strength indicator information is smaller than thearbitrary threshold x, since content reception has failed due to poormobile radio environment of the communication terminal, it can beforeseen that content reception will fail again even if multicastdelivery is performed again. Therefore, in this case, content receptionis performed by unicast delivery.

In this way, the communication terminal can circumvent an inefficientsituation in which a multicast reception is performed in a poor mobileradio environment where a high probability of lost packets isforeseeable and can make an efficient retransmission request. Inaddition, the base station-end can also significantly reduce the trafficload placed on communication paths by performing multicast deliveryrather than unicast delivery when possible to terminals in a favorablemobile radio environment.

Although the received signal strength indicator information indicatingpositive and negative aspects of the mobile environment is used in StepS404 as the received signal strength indicator of the communicationterminal during content reception failure, other methods can beimplemented as well. For example, the calculated average value of thereceived signal strength indicator from m seconds to n seconds prior tothe start of content reception can be used; the mobile radio environmentstate can be judged from the number of antenna bars; or the receivedsignal strength indicator information used to calculate the number ofantenna bars can be used.

Furthermore, fluctuations in the received signal strength indicators, ornamely, the received signal strength indicator variation, can becalculated by calculating a standard deviation of the received signalstrength indicator from i seconds to j seconds prior to the start ofcontent reception. Then, whether multicast reception is performed orunicast reception is performed can be judged using the standarddeviation as a threshold. If the standard deviation is large, thevariation in the received signal strength indicators is significant.Accordingly, the mobile radio environment is determined to be unstableand thus, unicast reception is performed.

On the other hand, if the standard deviation is small, the variation inthe received signal strength indicators is small. Accordingly, themobile radio reception is determined to be stable and thus, multicastreception is performed. In addition, whether to perform multicastreception or unicast reception can be judged by a combination of thereceived signal strength indicator and the standard deviation allowing amore reliable judgment.

After the content reception is judged to be successful at Step S401, thecontent reception completion judgment section performs notification tothe display section via the user interface section 305 to inform theuser that file reception was successful, such as displaying “successfulcontent reception”. A display such as that shown in reference number 501in FIG. 5B can be performed.

Service with enhanced user-friendliness can be provided to the user byperforming a display as such. In addition, the user can select whetherto display such information as desired by the input section 306. Servicewith enhanced user-friendliness can be provided to the user by allowingthe selection of whether to perform such displays.

In addition, after the content reception is judged to have failed atStep S401, the content reception completion judgment section performsnotification to the display section via the user interface section 305to inform the user that file reception failed, such as displaying“content reception failed”. A display such as that shown in referencenumber 500 in FIG. 5A can be performed. Furthermore, if the deliverysource simultaneously gives notification of re-reception timeinformation, a display that notifies the user of the next reception timecan be performed as shown in the reference number 500 in FIG. 5A.

Service with enhanced user-friendliness can be provided to the user byperforming displays as such. In addition, the user can select whether todisplay such information as desired by the input section 306. Servicewith enhanced user-friendliness can be provided to the user by allowingthe selection of whether to perform such displays.

Although the content reception method is judged using the receivedsignal strength indicator information at Step S404, the remainingbattery level can also be used. In the case that the remaining batterylevel is higher than a certain threshold, or namely, the terminal canstill be driven for a long period, multicast reception is performed.Furthermore, in the case that the remaining battery level is lower thana certain threshold, or namely, the terminal cannot be driven for a longperiod, unicast reception that can almost certainly receive content isperformed. In this way, efficient power consumption can be performed anduser-friendliness can be enhanced. The present embodiment can beactualized by replacing all received signal strength indicatorinformation in FIG. 3 and FIG. 4 with the remaining battery level. Theprocessing flow in this case is the same as that using received signalstrength indicator information.

In addition, when the remaining battery level is lower than a certainthreshold, or namely, when the terminal cannot be driven for a longperiod, unicast reception that can almost certainly receive contentmaybe performed. However, when the remaining battery level is higherthan a certain threshold, or namely, when the terminal can still bedriven for a long period, multicast reception should not be necessarilyperformed. This is because it cannot be said with certainty that theprobability of a successful completion of a multicast content receptionis high in a terminal that is in a poor mobile radio environmentregardless of a high remaining battery level.

Therefore, when the remaining battery level is higher than a certainthreshold, or namely, when the terminal can be driven for a long period,it is effective for the terminal whether multicast reception isperformed or unicast reception is performed should be determined againby using the received signal strength indicator information as describedin the second embodiment. In other words, the judgment of whetherunicast reception is performed or multicast reception is performed whenreceiving content in a content reception system comprising two receptionfunctions, the multicast reception and the unicast reception, is madeusing remaining battery level information and received signal strengthindicator information, and thus, the terminal of this invention canrealize further reduction in the power consumption of the terminal andto provide a more efficient service to the user.

As explained above, the present invention can select an optimalreception system and reduce reception failure because whether to usemulticast reception or unicast selection can be switched dynamically inconsideration of the mobile radio environment condition of eachterminal. In addition, by performing a dynamic switching of thereception method as such, the base station-end can perform multicastdelivery rather than unicast delivery when possible to communicationterminals in favorable mobile radio environments, thereby significantlyreducing the traffic load placed on communication paths.

In addition, the power consumption of the terminal can be furtherreduced and a more efficient service can be provided to the user byusing the first embodiment and the second embodiment in combination.

While the present invention has been described with reference to thepreferred embodiments, it is intended that the invention be not limitedby any of the details of the description therein but includes all theembodiments which fall within the scope of the appended claims.

1. A communication terminal which is capable of receiving content files,comprising: a content reception time acquisition means for acquiring acontent reception time; a multicast reception means for receivingcontent by multicast delivery; a unicast reception means for receivingcontent by unicast delivery; a remaining battery level acquisition meansfor acquiring remaining battery level information on the remainingbattery level for driving the communication terminal; a remainingbattery level acquisition time calculation means for calculating thetime at which the remaining battery level information is acquired usingthe content reception time information; a remaining battery levelacquisition time judgment means for judging whether the current time isthe time at which the remaining battery level information is acquired;and a reception method judgment means for selecting either the multicastreception means or the unicast reception means according to a judgmentresult of a reception method selection using the remaining battery levelinformation and instructing content reception.
 2. A communicationterminal which is capable of receiving content files, comprising: amulticast reception means for receiving content by multicast delivery; aunicast reception means for receiving content by unicast delivery; acontent reception completion judgment means for judging whether acontent reception was successful; a remaining battery level acquisitionmeans for acquiring remaining battery level information on the remainingbattery level for driving the communication terminal; and a receptionmethod judgment means for selecting either the multicast reception meansor the unicast reception means according to a judgment result of areception method selection using the remaining battery level informationand instructing content reception when the content reception completionjudgment means judges that the content reception was not completedsuccessfully.
 3. The communication terminal according to claim 2,further comprising: a display means for providing a user with variousinformation; a content reception completion judgment means for judgingwhether a content reception was successful; a display control means fordisplaying a notification of a successful content reception in thedisplay means when the content reception completion judgment meansjudges that the content reception was completed successfully.
 4. Thecommunication terminal according to claim 2, further comprising: adisplay means for providing a user with various information; a contentreception completion judgment means for judging whether a contentreception was successful; and a display control means for displaying anotification of a content reception failure in the display means whenthe content reception completion judgment means judges that the contentreception was completed abnormally.
 5. The communication terminalaccording to claim 2, further comprising: a content reception completionjudgment means for judging whether a content reception was successful; acontent reception time storage means for receiving and storing contentre-reception time; and a display control means for displaying thecontent re-reception time in the display means when the contentreception completion judgment means judges that the content receptionwas completed abnormally.